Pericyte involvement in capillary sprouting during angiogenesis in situ

Abstract

To investigate the participation of microvascular pericytes in the process of capillary sprouting, we examined whole-mount preparations of the rat mesentery by use of a double immunofluorescence approach. Angiogenesis was induced by intraperitoneal injections of either the mast cell-degranulating substance compound 48/80 or tumor cell-conditioned medium. Capillary sprouts were visualized by staining with rhodamine-conjugated phalloidin and pericytes were simultaneously stained by an antibody to the intermediate filament protein desmin. Developing pericytes were negative for the smooth-muscle isoform of alpha-actin, but were clearly reactive for desmin. Pericytes appear to be involved in the earliest stages of capillary sprouting. Pericytes were regularly found lying at and in front of the advancing tips of endothelial sprouts. At many sites pericytes were seen to bridge the gap between the leading edges of opposing endothelial sprouts, which were apparently preparing to merge, suggesting that pericytic processes may serve as guiding structures aiding outgrowth of endothelial cells.

Spatio-temporal analysis of vascular endothelial growth factor expression and blood vessel remodelling in pig ovarian follicles during the periovulatory period

“…The mural cells showed a different destiny in the two networks. On the basis of -SMA and vWF coexpression (Nehls et al 1992, Redmer et al 2001 and their location within microvessels, mural cells distributed along the inner network can be classified as pericytes (Nehls et al 1992). As shown in other tissues, pericyte processes penetrate the basement membrane to directly contact the underlying endothelium and, in a reciprocal manner, endothelial processes penetrate into the pericytes (Tilton et al 1979) as also observed in the inner network of periovulatory follicles.…”

“…It has been hypothesized that mural cells are generated by in situ differentiation of mesenchymal precursors at the time of endothelial sprouting (Nehls et al 1992). Other studies using an Figure 5 A representative example of double immunohistochemical localization of the endothelial cell marker, vWF (red stain) and of the cell proliferation marker, Ki-67 antigen (green stain).…”

Chapter 12 Structure of Microvascular Networks in Genetic Hypertension

“…For example, SM α-actin can be expressed by pericytes, immature smooth muscle cells, which express SM α-actin and not SM myosin heavy chain, and mature smooth muscle cells, which express both contractile proteins (Nehls and Drenckhahn, 1991;Price et al, 1994;Van Gieson et al, 2003;Yoshida and Owens, 2005). Desmin and PDGF-β can also be expressed by smooth muscle cells and interstitial fibroblasts (Nehls et al, 1992). Further complicating the issue of pericyte identification, expression of the various markers differs depending on species, tissue, and even developmental stage.…”

Pathological angiogenesis is reduced by targeting pericytes via the NG2 proteoglycan

“…Most of these strategies have focused on targeting endothelial cells, which form the inner lining of the vascular tube and are by far the best understood component of neovasculature. However, the walls of typical angiogenic microvessels have a second cellular component: namely, pericytes (mural cells) which form an outer sheath around the endothelium [2,5,6]. Much less is known about these perivascular cells, as evidenced by the 115-fold difference in the number of publications on endothelial cells and pericytes, respectively (revealed by a recent search of the PUBMED database).…”